You're being a good friend, keep doing what you are doing. I've been through this and I loved my 2 friends like you who were there for me.
Calls are nice, normal conversations to take your mind off things. The 2 week wait is awful. She'll feel as helpless as you! 
Listening when they want to vent. You don't have to agree, disagree or anything, just listen.
Advising friend to go easy on herself. So, treating herself (or if you can afford) to a manicure, a nice bag etc. I recently sent my friend a 'care package' which included magazines chocolate, hair mask, face mask, 4head stuff (she was getting bad headaches), notebook to write things down and a little nail varnish. It arrived in time for the weekend and she too was on her 2ww. She loved it and relaxed that weekend.
Find things to make her laugh or giggle. I sent my friend links to some classics threads on here. She loved them 
At the end of the 2ww, even if pregnant, very early days. She'll still be anxious. Just be aware of that and let her take one day at a time.